VirtualBox.exe pegs CPU when guest idle

Description

A Windows XP Pro SP2 guest running on a Windows XP Pro SP2 host causes VirtualBox.exe on the host to consume 90% of the CPU even though the guest is idle and its task manager shows CPU usage 1 or 2%. Process Explorer from Sysinternals shows that the call stack of the offending thread in VirtualBox.exe is usually one of the following: